Magnet keeper assembly method

ABSTRACT

A magnet assembly ( 200 ) is provided that comprises a magnet keeper ( 204 ) configured to hold at least one magnet ( 202 ). The bracket ( 208 ) is configured to receive the magnet keeper ( 204 ) and also configured to be attachable to a flowmeter ( 5 ) sensor assembly ( 10 ). A first surface ( 216 ) is formed on the magnet keeper ( 204 ), and a second surface ( 218 ) is formed on the bracket ( 208 ), wherein the first and second surfaces ( 216, 218 ) are configured to mate so to provide a radial alignment of the magnet keeper ( 204 ) that is within a predefined radial tolerance range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional application of and claims the benefit of U.S.patent application Ser. No. 14/479,600, filed on Sep. 8, 2014, entitled“Magnet keeper Assembly and Related Method,” which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to sensors, and more particularly tomethods related to a magnet keeper assembly for a vibrating sensor.

BACKGROUND OF THE INVENTION

Vibrating sensors, such as for example, vibrating densitometers andCoriolis flowmeters are generally known, and are used to measure massflow and other information related to materials flowing through aconduit in the flowmeter. Exemplary flowmeters are disclosed in U.S.Pat. No. 4,109,524, U.S. Pat. No. 4,491,025, and Re. 31,450, all to J.E. Smith et al. These flowmeters have one or more conduits of a straightor curved configuration. Each conduit configuration in a Coriolis massflowmeter, for example, has a set of natural vibration modes, which maybe of simple bending, torsional, or coupled type. Each conduit can bedriven to oscillate at a preferred mode.

Some types of mass flowmeters, especially Coriolis flowmeters, arecapable of being operated in a manner that performs a direct measurementof density to provide volumetric information through the quotient ofmass over density. See, e.g., U.S. Pat. No. 4,872,351 to Ruesch for anet oil computer that uses a Coriolis flowmeter to measure the densityof an unknown multiphase fluid. U.S. Pat. No. 5,687,100 to Buttler etal. teaches a Coriolis effect densitometer that corrects the densityreadings for mass flow rate effects in a mass flowmeter operating as avibrating tube densitometer.

Material flows into the flowmeter from a connected pipeline on the inletside of the flowmeter, is directed through the conduit(s), and exits theflowmeter through the outlet side of the flowmeter. The naturalvibration modes of the vibrating system are defined in part by thecombined mass of the conduits and the material flowing within theconduits.

When there is no flow through the flowmeter, a driving force applied tothe conduit(s) causes all points along the conduit(s) to oscillate withidentical phase or with a small “zero offset”, which is a time delaymeasured at zero flow. As material begins to flow through the flowmeter,Coriolis forces cause each point along the conduit(s) to have adifferent phase. For example, the phase at the inlet end of theflowmeter lags the phase at the centralized driver position, while thephase at the outlet leads the phase at the centralized driver position.Pickoffs on the conduit(s) produce sinusoidal signals representative ofthe motion of the conduit(s). Signals output from the pickoffs areprocessed to determine the time delay between the pickoffs. The timedelay between the two or more pickoffs is proportional to the mass flowrate of material flowing through the conduit(s).

Meter electronics connected to the driver generate a drive signal tooperate the driver and also to determine a mass flow rate and/or otherproperties of a process material from signals received from thepickoffs. The driver may comprise one of many well-known arrangements;however, a magnet and an opposing drive coil have received great successin the flowmeter industry. An alternating current is passed to the drivecoil for vibrating the conduit(s) at a desired conduit amplitude andfrequency. It is also known in the art to provide the pickoffs as amagnet and coil arrangement very similar to the driver arrangement.However, while the driver receives a current which induces a motion, thepickoffs can use the motion provided by the driver to induce a voltage.The magnitude of the time delay measured by the pickoffs is very small;often measured in nanoseconds. Therefore, it is necessary to have thetransducer output be very accurate.

The driver, as noted, often has a magnet mounted to a conduit with anopposing coil mounted to an opposing conduit. An alternating current ispassed through the coil, which results in the vibrating of bothconduits. The pickoffs are similarly constructed and oriented, exceptthat they generate alternating current signals as a result ofdriver-produced vibrations that are detected by the pickoffs. Bothdrivers and pickoffs may have magnet keepers that are mounted tobrackets which are typically welded or brazed onto the conduits. Itwould be ideal to braze the magnet keeper directly to the brackets, butthe heat necessary to braze the brackets to the conduits may causemagnets within the magnet keeper to lose field strength.Post-magnetizing an entire flowmeter or sensor assembly is notpractical. Therefore, the magnet keepers are attached to brackets thatare pre-attached to conduits. Unfortunately, this attachment yieldsresults in alignment inaccuracies due to the tolerances of the fastenersinvolved in the attachment. The present embodiments are directed tomethods to precisely attach magnet keepers to brackets, and therebyovercome these and other problems, and an advance in the art isachieved.

SUMMARY OF THE INVENTION

A method of forming a magnet assembly is provided according to anembodiment. The embodiment comprises the steps of: threading a magnetkeeper to define a first threaded region; threading a bracket that isconfigured to be attachable to a flowmeter sensor assembly to define asecond threaded region, wherein the second threaded region is configuredto engage the first threaded region; forming a first surface on themagnet keeper proximate the first threaded region; and forming a secondsurface on the bracket proximate the second threaded region, wherein thesecond surface is configured to engage the first surface when the magnetkeeper is threaded to the bracket so to provide a radial alignment ofthe magnet keeper that is within a predefined radial tolerance range.

Aspects

According to an aspect a method of forming a magnet assembly isprovided. The aspect comprises the steps of: threading a magnet keeperto define a first threaded region; threading a bracket that isconfigured to be attachable to a flowmeter sensor assembly to define asecond threaded region, wherein the second threaded region is configuredto engage the first threaded region; forming a first surface on themagnet keeper proximate the first threaded region; and forming a secondsurface on the bracket proximate the second threaded region, wherein thesecond surface is configured to engage the first surface when the magnetkeeper is threaded to the bracket so to provide a radial alignment ofthe magnet keeper that is within a predefined radial tolerance range. Athird surface is formed on the magnet keeper proximate the firstthreaded region; and forming a fourth surface on the bracket proximal tothe bracket's threads, wherein the fourth surface is configured toengage the third surface when the magnet keeper is threaded to thebracket so to provide a radial alignment of the magnet keeper that iswithin a predefined radial tolerance range.

Preferably, the second surface is disposed proximate a distal end of thebracket.

Preferably, the predefined radial tolerance range is between about 0.0inches and 0.002 inches.

Preferably, the first surface and second surface comprise a first set ofmating diameters.

Preferably, the third surface and fourth surface comprise a second setof mating diameters.

Preferably, the first set of mating diameters are smaller than thesecond set of mating diameters.

Preferably, the aspect comprises the steps of: forming a first threadrelief in the bracket disposed proximate a distal end of the threads;and forming a second thread relief in the bracket disposed proximate aproximal end of the threads.

Preferably, the aspect comprises the step of forming a travel stop onthe bracket.

Preferably, the aspect comprises the step of forming a locating face onthe magnet keeper configured to engage the travel stop to provide anaxial alignment of the magnet keeper that is within a predefined axialtolerance.

Preferably, the predefined axial tolerance is between about 0.0 inchesand 0.005 inches.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art flowmeter;

FIG. 2 shows a prior art meter electronics;

FIG. 3 shows a sensor assembly according to an embodiment;

FIG. 4 is a cross-section of the sensor assembly of FIG. 3;

FIG. 5 illustrates a magnet keeper according to an embodiment;

FIG. 6 is a cross-section of a magnet assembly according to anembodiment; and

FIG. 7 is a flow chart illustrating a method according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-7 and the following description depict specific examples toteach those skilled in the art how to make and use the best mode of theinvention. For the purpose of teaching inventive principles, someconventional aspects have been simplified or omitted. Those skilled inthe art will appreciate variations from these examples that fall withinthe scope of the invention and that the features described below can becombined in various ways to form multiple variations of the invention.As a result, the invention is not limited to the specific examplesdescribed below, but only by the claims and their equivalents.

FIG. 1 illustrates a prior art flowmeter 5, which can be any vibratingmeter, such as a Coriolis flowmeter or densitometer, for example withoutlimitation. The flowmeter 5 comprises a sensor assembly 10 and meterelectronics 20. The sensor assembly 10 responds to mass flow rate anddensity of a process material. Meter electronics 20 are connected to thesensor assembly 10 via leads 100 to provide density, mass flow rate, andtemperature information over path 26, as well as other information. Thesensor assembly 10 includes flanges 101 and 101′, a pair of manifolds102 and 102′, a pair of parallel conduits 103 (first conduit) and 103′(second conduit), a driver 104, a temperature sensor 106 such as aresistive temperature detector (RTD), and a pair of pickoffs 105 and105′, such as magnet/coil pickoffs, strain gages, optical sensors, orany other pickoff known in the art. The conduits 103 and 103′ have inletlegs 107 and 107′ and outlet legs 108 and 108′, respectively. Conduits103 and 103′ bend at least one symmetrical location along their lengthand are essentially parallel throughout their length. Each conduit 103,103′, oscillates about axes W and W′, respectively.

The legs 107, 107′, 108, 108′ of conduits 103,103′ are fixedly attachedto conduit mounting blocks 109 and 109′ and these blocks, in turn, arefixedly attached to manifolds 102 and 102′. This provides a continuousclosed material path through the sensor assembly 10.

When flanges 101 and 101′ are connected to a process line (not shown)that carries the process material that is being measured, materialenters a first end 110 of the flowmeter 5 through a first orifice (notvisible in the view of FIG. 1) in flange 101 and is conducted throughthe manifold 102 to the conduit mounting block 109. Within the manifold102, the material is divided and routed through conduits 103 and 103′.Upon exiting conduits 103 and 103′, the process material is recombinedin a single stream within manifold 102′ and is thereafter routed to exita second end 112 connected by flange 101′ to the process line (notshown).

Conduits 103 and 103′ are selected and appropriately mounted to theconduit mounting blocks 109 and 109′ so as to have substantially thesame mass distribution, moments of inertia, and Young's modulus aboutbending axes W-W and W′-W′, respectively. Inasmuch as the Young'smodulus of the conduits 103, 103′ changes with temperature, and thischange affects the calculation of flow and density, a temperature sensor106 is mounted to a conduit 103, 103′ to continuously measure thetemperature of the conduit. The temperature of the conduit, and hencethe voltage appearing across the temperature sensor 106 for a givencurrent passing therethrough, is governed primarily by the temperatureof the material passing through the conduit. The temperature-dependentvoltage appearing across the temperature sensor 106 is used in awell-known method by meter electronics 20 to compensate for the changein elastic modulus of conduits 103, 103′ due to any changes in conduit103, 103′ temperature. The temperature sensor 106 is connected to meterelectronics 20.

Both conduits 103, 103′ are driven by a driver 104 in oppositedirections about their respective bending axes W and W′ at what istermed the first out-of-phase bending mode of the flowmeter 5. Thedriver 104 may comprise any one of many well-known arrangements, such asa magnet mounted to a conduit 103′ and an opposing coil mounted to aconduit 103, through which an alternating current is passed forvibrating both conduits. A suitable drive signal is applied by meterelectronics 20, via lead 113, to the driver 104. It should beappreciated that while the discussion is directed towards two conduits103, 103′, in other embodiments, only a single conduit may be provided.It is also within the scope of the present invention to produce multipledrive signals for multiple drivers.

Meter electronics 20 receive the temperature signal on lead 114, and theleft and right velocity signals appearing on leads 115 and 115′,respectively. Meter electronics 20 produce the drive signal appearing onlead 113 to driver 104 and vibrate conduits 103, 103′. Meter electronics20 process the left and right velocity signals and the temperaturesignal to compute the mass flow rate and the density of the materialpassing through sensor assembly 10. This information, along with otherinformation, is applied by meter electronics 20 over path 26 toutilization means. An explanation of the circuitry of the meterelectronics 20 is not needed to understand the present invention and isomitted for brevity of this description. It should be appreciated thatthe description of FIG. 1 is provided merely as an example of theoperation of one possible vibrating meter and is not intended to limitthe teaching of the present invention.

A Coriolis flowmeter structure is described although it will be apparentto those skilled in the art that the present invention could bepracticed on a vibrating tube densitometer without the additionalmeasurement capability provided by a Coriolis mass flowmeter. In fact,the present invention may be utilized in pipelines, conduits, flanges,of all sizes, with or without means for measuring mass flow, density,etc.

FIG. 2 illustrates an example of prior art meter electronics 20. Themeter electronics 20 can include an interface 301 and a processingsystem 303. The processing system 303 may include a storage system 304.The storage system 304 may comprise an internal memory, and/or maycomprise an external memory. The meter electronics 20 can generate adrive signal 311 and supply the drive signal 311 to the driver 104. Inaddition, the meter electronics 20 can receive sensor signals 310 fromthe sensor assembly 10, such as pickoff/velocity sensor signals, strainsignals, optical signals, temperature signals, or any other signalsknown in the art. The meter electronics 20 can operate as a densitometeror can operate as a mass flowmeter, including operating as a Coriolisflowmeter. It should be appreciated that the meter electronics 20 mayalso operate as some other type of vibrating sensor assembly and theparticular examples provided should not limit the scope of the presentinvention. The meter electronics 20 can process the sensor signals 310in order to obtain flow characteristics of the material flowing throughthe flow conduits 103, 103′. In some embodiments, the meter electronics20 may receive a temperature signal 312 from one or more RTD sensors orother temperature sensors 106, for example.

The interface 301 can receive the sensor signals 310 from the driver 104or pickoffs 105, 105′, via leads 113, 115, 115′, respectively. Theinterface 301 may perform any necessary or desired signal conditioning,such as any manner of formatting, amplification, buffering, etc.Alternatively, some or all of the signal conditioning can be performedin the processing system 303. In addition, the interface 301 can enablecommunications between the meter electronics 20 and external devices.The interface 301 can be capable of any manner of electronic, optical,or wireless communication.

The interface 301 in one embodiment can include a digitizer 302, whereinthe sensor signal comprises an analog sensor signal. The digitizer 302can sample and digitize the analog sensor signal and produce a digitalsensor signal. The digitizer 302 can also perform any needed decimation,wherein the digital sensor signal is decimated in order to reduce theamount of signal processing needed and to reduce the processing time.

The processing system 303 can conduct operations of the meterelectronics 20 and process flow measurements from the sensor assembly10. The processing system 303 can execute one or more processingroutines, such as a density routine 313, a zero routine 314, anoperating routine 315, and a flow rate routine 316 for example withoutlimitation. According to an embodiment, the meter electronics 20 canalso measure a temperature signal 312, and associate that temperaturewith the flow rates captured at a given temperature.

The flowmeter 5 may generate a density 317. A mass flow rate 318 or thedensity 317 may be calculated, for example, as part of the operatingroutine 315. In an embodiment, the temperature signal 312 is read and azero-flow rate is also saved and calculated as part of the zero routine314. A calibrated meter zero improves calculation accuracy.

The processing system 303 can comprise a general purpose computer, amicro-processing system, a logic circuit, or some other general purposeor customized processing device. The processing system 303 can bedistributed among multiple processing devices. The processing system 303can include any manner of integral or independent electronic storagemedium, such as the storage system 304.

The processing system 303 processes the sensor signal 310 in order togenerate the drive signal 311, among other things. The drive signal 311is supplied to the driver 104 in order to vibrate the associatedconduit(s), such as the conduits 103, 103′ of FIG. 1.

It should be understood that the meter electronics 20 may includevarious other components and functions that are generally known in theart. These additional features are omitted from the description and thefigures for the purpose of brevity. Therefore, the present inventionshould not be limited to the specific embodiments shown and discussed.

FIG. 3 shows a sensor assembly 10 according to an embodiment. A driver104 and pickoffs 105, 105′ are illustrated. Since the driver 104 andpickoffs 105, 105′ are constructed as coil/magnet combinations, theywill collectively be referred to as magnet assemblies 200. FIG. 4 is across-sectional view of a magnet assembly 200. The magnet assembly 200,according to an embodiment, includes at least one magnet 202 and amagnet keeper 204. The magnet 202 in the embodiment shown issubstantially cylindrical. However, other magnet shapes can be employed.The magnet 202 can be composed of one or more magnets. The magnet 202can comprise a stack of magnets that are attached together, for example.The magnet 202 in one embodiment comprises a samarium cobalt (SmCo)magnet. A SmCo magnet substantially retains its magnetic properties athigh temperatures and therefore is advantageous in use with a flow meterthat receives a high temperature flow material. For example, at or above400° F., a SmCo magnet can generate a satisfactory level of the magneticflux needed to operate in a magnet assembly 200. However, it should beunderstood that other magnet materials can be used and are within thescope of the description and claims, such as an AlNiCo magnet, forexample, without limitation. Additionally, the magnet may be coated orplated, according to needs. In an embodiment, the magnet 202 isnickel-plated.

With continuing reference to FIGS. 3-4 and also FIG. 5, the magnetkeeper 204 comprises a first threaded region 210. In an embodiment, thefirst threaded region 210 is oriented orthogonally to a magnet-receivingface 206. The first threaded region 210 is formed with the magnet keeper204, and in an embodiment is machined. A bracket 208 is attachable tothe conduit 103. The bracket 208 may be brazed or welded to the conduit103 in an embodiment. However, it should be understood that the bracket208 can affix to a flowmeter 5 structure, and more particularly a sensorassembly 10 structure, in any manner. The bracket 208, in the embodimentshown, includes a second threaded region 212. The first and secondthreaded regions 210, 212 are complementary, and are used to removablyaffix the magnet keeper 204 to the bracket 208. It should be understood,however, that the magnet keeper 204 can be attached to the bracket 208in any manner. For threaded embodiments, the threads may be ISO metricthreads, unified inch screw threads, pipe threads, taper pipe threads,American pipe threads, ACME threads, trapezoidal threads, buttress screwthreads, round threads, and any other thread known in the art.

FIGS. 4-5 and FIG. 6 show the magnet keeper 204 according to anembodiment. In this embodiment, the magnet-receiving face 206 includes acountersink region 214 that is configured to receive the magnet 202. Thecountersink region 214 aids in aligning and assembling the magnet 202.The countersink region 214 can advantageously function to center themagnet 202 on the magnet keeper 204. In addition, the countersink region214 can provide more area for attaching the magnet 202 to the magnetkeeper 204. The countersink region 214 can substantially match the shapeof the magnet 202.

The magnet assembly 200, according to any embodiment, can be constructedin various manners. In one method, the magnet 202 is placed against themagnet-receiving face 206 of the magnet keeper 204 and brazed in place.In another method, the magnet 202 is placed within the countersinkregion 214 of the magnet keeper 204 and brazed in place. In anothermethod, the magnet 202 is plated (such as with nickel, for examplewithout limitation) into place as a means of affixing the partstogether. Magnet keepers 204 and magnets 202 subjected to heat duringthe attachment process, such as for magnets 202 brazed or plated intoplace, for example without limitation, may then be subjected to are-magnetization process to restore magnetic capacity lost due to theheat of attachment processes.

In prior art embodiments, a magnet keeper is attached to a bracket witha fastener, such as a threaded bolt, for example. Unfortunately, thetypical run-out for a thread-form is in the range of about 0.007 inchesto 0.012 inches, which results in a relatively poor radial alignment. Inan embodiment, the radial alignment of the magnet keeper 204 is within apredefined radial tolerance range. In an embodiment, the predefinedradial tolerance range is between about 0.0 in. and 0.005 inches. In arelated embodiment, the predefined radial tolerance range is betweenabout 0.0 in. and 0.002 inches. To accomplish such tight tolerances,mating indexing surfaces are employed. In an embodiment, a first surface216 is formed on the magnet keeper 204, and this surface is configuredto engage a complementary second surface 218 formed on the bracket 208.A precise fit between the first and second surfaces 216, 218 facilitatesthe above-noted tight radial tolerance ranges. In an embodiment, thefirst and second surfaces 216, 218 are round, and comprise a first setof mating diameters, as is illustrated in FIGS. 4 and 6. Additionally,the second surface 218 may be oriented distally to the second threadedregion 212, such that the magnet keeper 204 will, upon installation, bemostly threaded or otherwise attached to the bracket 208 before thefirst and second surfaces 216, 218 engage.

In an embodiment, a third surface 220 is formed on the magnet keeper204, and this surface is configured to engage with a complementaryfourth surface 222 formed on the bracket 208. A precise fit between thethird and fourth surfaces 220, 222 also aids in facilitating theabove-noted tight radial tolerance ranges. In an embodiment, the thirdand fourth surfaces 220, 222 are round, and comprise a second set ofmating diameters, as is illustrated in FIGS. 4 and 6. The fourth surface222 may be oriented proximally to the second threaded region 212, suchthat the third and fourth surfaces 220, 222 will, upon installation, beengaged before the magnet keeper 204 is fully threaded or otherwiseattached to the bracket 208. The first and second set of matingdiameters may be the same diameter or different diameters. In anembodiment, the first set of mating diameters are smaller than thesecond set of mating diameters.

To facilitate precise fitment of the first and second surfaces 216, 218and third and fourth surfaces 220, 222, a thread relief 228 may beformed on the bracket 208 proximate each terminus of the second threadedregion 212. This ensures that radii associated with threaded surfaces donot interfere with the radial alignment of the magnet keeper 204 inrelation to the bracket 208. In an embodiment, there is a single threadrelief 228, and in another embodiment, there are two thread reliefs 228.

Besides radial alignment, axial alignment of the magnet keeper 204 is aconsideration. For this reason, in an embodiment, a travel stop 224 isformed on the bracket 208. The travel stop 224 is positioned such thatit defines a datum from which axial tolerances may be referenced. Alocating face 226 formed on the magnet keeper 204 is configured to indexagainst the travel stop 224 upon installation of the magnet keeper 204onto the bracket 208 such that the axial position of the magnet keeper204 is within a predefined axial tolerance range. In an embodiment, thepredefined axial tolerance range is between about 0.0 in. and 0.005inches.

Turning to FIG. 7, a method of forming a magnet assembly is providedaccording to an embodiment. In step 300, a magnet keeper 204 is threadedso to define a first threaded region 210. The bracket 208 is alsothreaded, as shown in step 302, to define a second threaded region 212.The second threaded region 212 and first threaded region 210 areconfigured to engage each other. The bracket 208 is also configured tobe attachable to a flowmeter 5 sensor assembly 10. The bracket 208 isbrazed or welded to the conduit 103 in an embodiment. It should beunderstood that the bracket 208 can be affixed to a flowmeter 5structure, such as the sensor assembly 10, for example, in any mannerknown in the art.

In step 304, a first surface 216 is formed on the magnet keeper 204proximate the first threaded region 210. This surface is complementaryto a second surface 218. In step 306, a second surface 218 is formed onthe bracket 208 proximate the second threaded region 212. As thesesurfaces are complementary, they are configured to engage each otherwhen the magnet keeper 204 is threaded onto the bracket 208. In anembodiment, the second surface 218 is disposed proximate a distal end ofthe bracket 208. These mating surfaces foster a radial alignment of themagnet keeper 204 that is within a predefined tolerance range. In anembodiment, the predefined radial tolerance range is between about 0.0inches and 0.002 inches. In an embodiment, the first and second surfaces216, 218 are shaped to form a first set of mating diameters.

In a related embodiment of a method, a third surface 220 is formed onthe magnet keeper 204 proximate the first threaded region 210, and afourth surface 222 is formed on the bracket 208 proximal to thebracket's threads. Similar to the first and second surfaces 216, 218,the third and fourth surfaces 220, 222 are configured to engage eachother when the magnet keeper 204 is threaded to the bracket 208, andthis similarly provides a radial alignment of the magnet keeper 204 thatis within a predefined tolerance range. In an embodiment, the thirdsurface and fourth surface 220, 222 comprise a second set of matingdiameters. It is contemplated that the first set of mating diameters maybe smaller than the second set of mating diameters.

In embodiments of a method of forming a magnet assembly, a thread relief228 in the bracket 208 is formed proximate a distal end of the secondthreaded region 212. Additionally, a thread relief 228 may be formed onthe bracket 208 proximate a proximal end of the second threaded region212. A travel stop 224 may be formed on the bracket 208 in anembodiment. The travel stop 224 is situated such that a locating face226 may engage the travel stop 224. The locating face 226 is formed onthe magnet keeper 204 in an embodiment. The travel stop 224 and locatingface 226 are configured to engage each other to provide an axialalignment of the magnet keeper 204 that is within a predefined axialtolerance. In an embodiment of a method, the predefined axial toleranceis between about 0.0 inches and 0.005 inches.

The detailed descriptions of the above embodiments are not exhaustivedescriptions of all embodiments contemplated by the inventors to bewithin the scope of the invention. Indeed, persons skilled in the artwill recognize that certain elements of the above-described embodimentsmay variously be combined or eliminated to create further embodiments,and such further embodiments fall within the scope and teachings of theinvention. It will also be apparent to those of ordinary skill in theart that the above-described embodiments may be combined in whole or inpart to create additional embodiments within the scope and teachings ofthe invention.

Thus, although specific embodiments of, and examples for, the inventionare described herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize. The teachings providedherein can be applied to other vibrating systems, and not just to theembodiments described above and shown in the accompanying figures.Accordingly, the scope of the invention should be determined from thefollowing claims.

We claim:
 1. A method of forming a magnet assembly, comprising the stepsof: threading a magnet keeper to define a first threaded region;threading a bracket that is configured to be attachable to a flowmetersensor assembly to define a second threaded region, wherein the secondthreaded region is configured to engage the first threaded region;forming a first surface on the magnet keeper proximate the firstthreaded region; forming a second surface on the bracket proximate thesecond threaded region, wherein the second surface is configured toengage the first surface when the magnet keeper is threaded to thebracket so to provide a radial alignment of the magnet keeper that iswithin a predefined radial tolerance range; forming a third surface onthe magnet keeper proximate the first threaded region; and forming afourth surface on the bracket proximal to the bracket's threads, whereinthe fourth surface is configured to engage the third surface when themagnet keeper is threaded to the bracket so to provide a radialalignment of the magnet keeper that is within a predefined radialtolerance range.
 2. The method of forming a magnet assembly of claim 1,wherein the second surface is disposed proximate a distal end of thebracket.
 3. The method of forming a magnet assembly of claim 1, whereinthe predefined radial tolerance range is between about 0.0 inches and0.002 inches.
 4. The method of forming a magnet assembly of claim 1,wherein the first surface and second surface comprise a first set ofmating diameters.
 5. The method of forming a magnet assembly of claim 4,wherein the third surface and fourth surface comprise a second set ofmating diameters.
 6. The method of forming a magnet assembly of claim 5,wherein the first set of mating diameters are smaller than the secondset of mating diameters.
 7. The method of forming a magnet assembly ofclaim 1, comprising the steps of: forming a first thread relief in thebracket disposed proximate a distal end of the threads; and forming asecond thread relief in the bracket disposed proximate a proximal end ofthe threads.
 8. The method of forming a magnet assembly of claim 1,comprising the step of forming a travel stop on the bracket.
 9. Themethod of forming a magnet assembly of claim 8, comprising the step offorming a locating face on the magnet keeper configured to engage thetravel stop to provide an axial alignment of the magnet keeper that iswithin a predefined axial tolerance.
 10. The method of forming a magnetassembly of claim 9, wherein the predefined axial tolerance is betweenabout 0.0 inches and 0.005 inches.